He had smashed his Kiwi victim's head against a table in the 24 hours before he murdered her, said the documentary, which screened at 10am today (NZ time).

It showed Turner strutting around a packed Bournemouth bar in a rage, smashing a glass off a table.

While the head-smashing incident took place off camera, Longley is shown holding her head, being helped from the table and consoled by her girlfriends.

One night later, in May 2011, she was choked to death in Turner's bedroom.

Channel 5 spent about 10 days in New Zealand making the documentary, and spoke to Mark Longley and Emily's mother, Caroline.

The documentary contains the 999 call Turner's mother made 40 minutes after Emily was found dead, in an attempt to conceal her son's crime.

Turner's parents were both jailed for perverting the course of justice. None of the family has shown remorse, which has upset the Longley family.

After her son had killed Longley in his bedroom, Anita Turner, 51, said the Auckland-raised youngster may have been choked by a tight necklace.

Leigh Turner destroyed a letter his son wrote confessing to the crime.

Turner's friends said Turner was enraged and paranoid that Longley was seeing other men. Channel 5 shows him as a maniac intent on killing her.

Turner was jailed in May 2012 for at least 16 years, for the murder. He was also sentenced in Winchester Crown Court to nine months' jail for perverting the course of justice. The terms were concurrent.

His appeal against that sentence was this year rejected in the High Court at London. Lord Chief Justice Baron Igor Judge, Mr Justice Royce and Mr Justice Globe spent just five minutes deliberating.

Defence counsel Anthony Donne, QC, had contended that some of the 300 hours of police covert surveillance recordings made from May 18 to June 14, 2011, at Turner's home contained legally privileged material and were grounds for overturning the conviction.

Turner was reportedly beaten up in jail and had his cell torched after he plastered pictures of Longley on his cell walls and talked about the day he would be set free from Swaleside prison in Kent, to a life of "champagne, Bentleys and birds".

Turner also showed other inmates mail he said was sent by "fans", which led to him being bashed.

A source at the prison told a newspaper: "Turner is a gobby little prick who has had it coming for some time."